Base Buffering Capacity Research Articles

The longevity evaluation of multi-metal stabilization by MgO in Pb/Zn smelter-contaminated soils.

The re-mobilization risks of potentially toxic elements (PTEs) during stabilization deserve to be considered. In this study, artificial simulation evaluation methods based on the environmental stress of freeze-thaw (F-T), acidification and variable pH were conducted to assess the long-term effectiveness of PTEs stabilizedby MgO in Pb/Zn smelter contaminated soils. Among common stabilizingmaterials, MgO was considered asthe best remediation material, since PTEs bioavailability reduced by 55.48% for As, 19.58% for Cd, 10.57% for Cu, and 26.33% for Mn, respectively. The stabilization effects of PTEs by MgO were best at the dosage of 5 wt%, but these studied PTEswould re-mobilize after 30 timesF-T cycles. Acid and base buffering capacity results indicated that the basicity of contaminated soils with MgO treatment reduced under F-T action, and the leachedPTEs concentrations would exceed the safety limits of surface water quality standard in China (GB3838-2002) after acidification of2325 years. No significant changes were foundin thepH-dependent patterns of PTEs before and after F-Tcycles. However, after F-Tcycles, the leaching concentrations of PTEs increased due to the destruction of soil microstructure and the functionality of hydration products formed by MgO, as indicated by scanning electron microscopy (SEM)coupled withenergydispersive Xray spectroscopy (EDS) results. Hence, these findings would provide beneficial references for soil remediation assessments ofcontaminated soils under multi-environmental stress.

Preparation of an amphiphilic peptide (P13) with proton sponge effect and analysis of its antitumor activity

In order to prevent drugs from being captured and degraded by the acidic environment of organelles, such as lysosomes, after entering cells, this study designed and synthesized a novel carrier amphiphilic polypeptide (DGRHHHLLLAAAA), designated P13, for use as a tumor-targeting drug delivery vehicle. The P13 peptide was synthesized by the solid phase synthesis method, and its self-assembly behavior and drug-loading capacity in aqueous solution were studied and characterized in vitro. Doxorubicin (DOX) was loaded by dialysis method, and P13 and DOX were mixed at a mass ratio of 6:1 to form regular rounded globules. The acid–base buffering capacity of P13 was investigated determined by acid–base titration. The results revealed that P13 had excellent acid–base buffering capacity, a critical micelle concentration value of about 0.000 21 g l−1, and the particle size of P13-Dox nanospheres was 167 nm. The drug encapsulation efficiency and drug loading capacity of micelles were 20.40 ± 1.21% and 21.25 ± 2.79%, respectively. At the concentration of 50 μg ml−1 of P13-DOX , the inhibition rate was 73.35%. The results of the in vivo antitumor activity assay in mice showed that P13-DOX also exhibited excellent inhibitory effect on tumor growth, compared with the tumor weight of 1.1 g in the control group, the tumor weight in the P13-DOX-treated group was only 0.26 g. Additionally, the results of hematoxylin and eosin staining of the organs showed that P13-DOX had no damaging effect on normal tissues. The novel amphiphilic peptide P13 with proton sponge effect designed and prepared in this study is expected to be a promising tumor-targeting drug carrier with excellent application potential.

Yogurt and molasses can alter microbial-digestive and nutritional characteristics of pomegranate leaves silage

Fewer studies in recent years have been conducted on the nutritional potential and fermentation quality of silage prepared from pomegranate leaves (PL). So, we investigated the nutritional-fermentation quality of PL before and after ensiling with or without yogurt containing mainly lactic acid-producing bacteria (Lactobacillus bulgaricus and Streptococcus thermophiles) and molasses (at two levels of 2 and 4% of dry matter) in the polyethylene microsilos for 60 days. A range of dry matter (29.1–39.1%), crude protein (3.85–4.83%), ash (5.33–8.60%), and non-fiber carbohydrates (53.2%–58.6%) contents were observed among the treatments. A significant increase in calcium, potassium, magnesium, manganese, iron, and zinc was observed in PL after ensiling compared to before ensiling (p < 0.05). The PL ensiled with 4% yogurt exhibited the highest ammonia nitrogen, lactic and acetic acids, but the lowest butyric acid among the ensiled PL (p < 0.05). The ensiling of PL without additive (control) significantly decreased potential gas production, dry matter digestibility, organic matter digestibility, total volatile fatty acids, metabolizable energy, net energy for lactation, base-buffering capacity, titratable alkalinity, and acid–base buffering capacity compared to before ensiling (p < 0.05). According to the present results, the nutritional value of PL before ensiling was higher than after ensiling. The addition of yogurt and molasses to PL at the ensiling process especially at 4% of dry matter, improved the fermentation and nutritional characteristics. In general, the addition of yogurt or molasses as two cheap and available additives is recommended to improve the digestive-fermentation parameters of PL in silo and ruminal environments.

Physicochemical indicators of dental patient saliva who have undergone an uncomplicated coronavirus infection

Today, it has been proven that saliva is the main medium through which the new COVID-19 coronavirus infection spreads. Since the oral cavity is the gateway for the SARS-CoV-2 virus, the degree of change in the physicochemical parameters of the saliva of people who have had coronavirus infection compared to people who have not had COVID-19 is of interest. This study involved dental patients of the first and second health groups with a history of chronic generalized periodontitis of moderate degree in the stage of remission. We studied physicochemical parameters of saliva such as pH, surface tension and base buffering capacity. The results of this stage of the study showed saliva acidification, that is a decrease in pH in people who had had a new coronavirus infection compared to the indicators of people from the control group. The average values of the surface tension of saliva in patients of the control group are 30% less than in those who have had COVID-19. This indicates that the saliva of people who have not been sick with the new coronavirus contains more surface-active agents (surfactants). Surfactants provide rinsing and disinfecting functions of saliva, therefore, it can be concluded that these functions are less pronounced in patients who have recovered from COVID-19. The base buffering capacity of the saliva of patients who have had COVID-19 is, on average, 35% higher than that of people from the control group. Thus, the pH and the base buffering capacity are in correlation: the lower the pH value, the higher the acidity of the saliva and the higher the base buffering capacity is. At the second stage of the study, similar physicochemical parameters of patients’ saliva were measured after the application of an oral spray containing a synthetic peptide (ZP2) of the active center of granulocyte-macrophage colony-stimulating factor. This spray was used as an antibacterial therapy for the oral cavity after professional hygiene of patients. In 5 minutes after spray irrigation, an increase in saliva pH was observed in all test subjects within the physiological norm. In patients, regardless of their anamnesis, the surface tension of saliva changed in different ways. In a number of people, it increased, which indicates an increase in the concentration of surfactants in saliva, while in others it decreased, which can be explained by the high rate of penetration of surfactants from saliva through the gums into the blood. After the application of the ZP-2 peptide, the base buffering capacity of saliva decreases or remains unchanged. In patients of the control group, the indicators of the base buffering capacity of saliva change less than in patients who have undergone COVID-19. All the studied physicochemical parameters of saliva in patients who had had uncomplicated COVID-19, three months after receiving two negative results for the SARS-CoV-2 virus, remained within the physiological norm.

A study on the nutritional characteristics of some plants and their effects on ruminal microbial fermentation and protozoa population

We designed this project to determine the nutritional potential and ruminal microbial fermentation properties of eight rangeland plants (Dracocephalum moldavica L., Melissa officinalis L., Ruta graveolens L., Perovskia abrotanoides Kar., Cichorium intybus L., Borago officinalis L., Peganum harmala L., and Teucrium polium L.) collected from the semi-arid region of Iran at two consecutive years (2019 and 2020) for ruminant diets. Medicago sativa as a common forage was also considered as control. We determined the chemical-mineral composition, buffering capacity, in vitro gas yield, ruminal fermentation, and protozoa population in a culture medium with the standard laboratory methods. A significant difference in chemical-mineral compounds was observed among the studied plants (p < 0.05). A lower crude protein range (6.28% for Cichorium intybus L. to 18.4% for Melissa officinalis L.) was observed rather than Medicago sativa (20.3%). The amount of calcium was highest in Peganum harmala L. (23.5–24.2 g/kg DM) and lowest in Ruta graveolens L. (1.15–1.25 g/kg DM). Dracocephalum moldavica L. exhibited the highest acid–base buffering capacity (235–242 mEq×10−3) among other plants. The highest decrease in total protozoa and other protozoan populations was observed when Perovskia abrotanoides Kar. was added to the culture medium. Teucrium Polium L. had the greatest potential gas yield and its total volatile fatty acid was comparable with Medicago sativa. It seems that eight plants are nutritionally suitable for partial replacement of the conventional plants such as Medicago sativa in diets of small ruminants, however dietary supplementation of Peganum harmala L. due to its alkaloids content should be done with caution.

Waste hazard properties HP 4 ‘Irritant’ and HP 8 ‘Corrosive’ by pH, acid/base buffer capacity and acid/base concentration

European "Technical Recommendations" have proposed, in addition to the use of substance concentrations, the use of a pH (≤ 2 or ≥ 11.5) and an acid / base buffering capacity to classify waste into according to their hazardous properties HP 4 'Irritant' and HP 8 'Corrosive'. Buffer capacity refers to a 2018 UK classification guide referring to the 'corrosive' level of a method proposed in 1988 for substances and preparations but not retained in EU regulations. The different methods of classifying products and wastes in terms of corrosivity or irritation are compared. The waste method using pH and buffering capacity is expressed as an acid / base concentration and compared to the product method (CLP). The “corrosive” level of 1988 corresponds to an average acid / base concentration ≥ 14.4Ͽie 14 times less severe than CLP (acid / base concentration ≥ 1Ͽ These methods were applied to five alkaline wastes (pH ≥ 11.5). Minimum pH waste is not classified by both methods, and three higher pH wastes are classified by both methods. Intermediate waste is classified by CLP but not by the proposed waste method. In order not to innovate and create a new divergence between products and waste, it seems preferable to use the product regulations for HP 4 and HP 8. Fortunately, the elimination of the danger HP 4 and HP 8 from acidic or alkaline waste can be obtained by neutralization (possibly by other wastes), including for alkaline wastes by (natural) carbonation by atmospheric CO2.

Surface charge of mesoporous calcium silicate and its adsorption characteristics for heavy metal ions

Mesoporous calcium silicate (MCS) was synthesized using the ultrasonic-assisted template method by using calcium nitrate tetrahydrate and sodium metasilicate nonahydrate as raw materials and cetyltrimethylammonium bromide–methenamine as the template. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller method were used for the characterization of MCS. The surface charge characteristics of MCS and its adsorption characteristics for Ni2+, Cu2+, Zn2+, Pb2+, Mn2+, and Cd2+ were also investigated. MCS formed through the accumulation of thin flakes with various shapes and exhibited a slit-pore structure and uneven surfaces with a specific surface area of 239.41 m2 g−1 and a pore size of 11.74 nm. MCS possessed a distinct, wide, near-zero potential point pH range of 5–9, and the point of zero charge, pHPZC, reached 8.6 ± 0.1. The MCS surface was alkaline, and MCS exhibited excellent acid–base buffering capacity at pH 5–11. The high adsorption capacity of MCS for the six heavy metal ions at pH 5.0–7.5 followed the order Pb2+ > Cd2+ > Zn2+ > Cu2+ > Ni2+ > Mn2+ (in mgg−1). The adsorption for the six heavy metal ions occurred rapidly and attained equilibrium within 120 min. The order of adsorption activation energy was Mn2+ > Zn2+> Ni2+ > Pb2+ > Cu2+ > Cd2+. The adsorption processes of the six heavy metal ions were all endothermic, entropy increasing, and spontaneous. MCS remained stable during adsorption, but the adsorbed heavy metal ions underwent transformation, especially Cu2+, Pb2+, and Cd2+, which formed new phases. The adsorption mechanisms included physical adsorption, chemical adsorption (particularly surface complexing adsorption and surface precipitation), and ion exchange. MCS exhibits an excellent adsorption and recycling performance and the potential to become an adsorption material with excellent properties for heavy metal ions.

Environmental aspects of the effect of earthworm (Lumbricidae, Oligochaeta) tropho-metabolic activity on the pH buffering capacity of remediated soil (steppe zone, Ukraine)

Environmental aspects of tropho-metabolic activity of soil saprophages on the pH-buffering capacity of remediated soils in Ukraine was considered. Earthworm (Lumbricidae) casts have been proven experimentally to have a higher acid–base buffering capacity in comparison with that of the initial soil. Remediated soils enriched with earthworm casts become more resistant to negative anthropogenic effects. Thus, the activity of soil saprophages influences positively the environmental properties of remediated soils on forest remediation sites by increasing their buffer capacity.

Biogeochemical processes and buffering capacity concurrently affect acidification in a seasonally hypoxic coastal marine basin

Abstract. Coastal areas are impacted by multiple natural and anthropogenic processes and experience stronger pH fluctuations than the open ocean. These variations can weaken or intensify the ocean acidification signal induced by increasing atmospheric pCO2. The development of eutrophication-induced hypoxia intensifies coastal acidification, since the CO2 produced during respiration decreases the buffering capacity in any hypoxic bottom water. To assess the combined ecosystem impacts of acidification and hypoxia, we quantified the seasonal variation in pH and oxygen dynamics in the water column of a seasonally stratified coastal basin (Lake Grevelingen, the Netherlands). Monthly water-column chemistry measurements were complemented with estimates of primary production and respiration using O2 light–dark incubations, in addition to sediment–water fluxes of dissolved inorganic carbon (DIC) and total alkalinity (TA). The resulting data set was used to set up a proton budget on a seasonal scale. Temperature-induced seasonal stratification combined with a high community respiration was responsible for the depletion of oxygen in the bottom water in summer. The surface water showed strong seasonal variation in process rates (primary production, CO2 air–sea exchange), but relatively small seasonal pH fluctuations (0.46 units on the total hydrogen ion scale). In contrast, the bottom water showed less seasonality in biogeochemical rates (respiration, sediment–water exchange), but stronger pH fluctuations (0.60 units). This marked difference in pH dynamics could be attributed to a substantial reduction in the acid–base buffering capacity of the hypoxic bottom water in the summer period. Our results highlight the importance of acid–base buffering in the pH dynamics of coastal systems and illustrate the increasing vulnerability of hypoxic, CO2-rich waters to any acidifying process.

Copper, lead and cadmium removal by Ca Al layered double hydroxides

Layered double hydroxides are increasingly studied as heavy metal scavengers due to their acid/base buffering capacity that leads to hydroxide precipitation. Their intercalation with ligands such as edta also provides active sites for heavy metal chelation to these solids. In this work, both mechanisms are studied in Ca–Al layered double hydroxides (LDHs) with a Friedel's salt layered structure and intercalated with either nitrate (Ca–Al–NO3) or [Ca(edta)]2− (Ca–Al–[Ca(edta)]). With this aim, the acid–base buffering capacity of these solids was determined and their removal behavior studied as a function of equilibrium concentration and pH. The solids presented high instability, Ca2+ ions being selectively leached at pH values as high as 8. As a consequence, high affinity and large removal capacity of Cu2+, Cd2+ and Pb2+ were obtained for Ca–Al–NO3 by a hydroxide precipitation mechanism. The removal capacity of Ca–Al–[Ca(edta)] was quite similar, however, a portion of heavy metal ions was solubilized due to [Ca(edta)]2− release. The heavy metal hydroxides obtained by the Ca–Al LDH removal action produced immobilization at pH values lower than those produced by simple alkalinization.

Absorption of SO2 from flue gas by aqueous fulvic acid solution

A new regenerable flue gas desulfurization process was proposed, in which fulvic acid derived from biomass residues was used as an absorbent to absorb SO2 from flue gas, based on acid–base buffering capacity. Experiments have been carried out to examine the absorption, desorption and reabsorption performance of fulvic acid solution in a lab-scale reactor. The results show fulvic acid solution (0.04 g mL−1, pH 5.5) could excellently absorb SO2 with a maximum absorption efficiency of 97.5% (298 K, 2200 ppm SO2, 5% O2, 0.14 m3 h−1). In the process of SO2 absorption, chemical absorption is the predominant mechanism. The SO2-loaded solution is readily desorbed and regenerated under ambient pressure by heating at 343 K, and the regenerated fulvic acid solution still exhibits good absorption performance after seven absorption/desorption cycles. Trace metal ions binding to fulvic acid play a decisive role in the absorption process. Fulvic acid samples before and after absorbing SO2 were well characterized by Fourier transform infrared spectroscopy, near-edge X-ray absorption fine structure and X-ray photoelectron spectroscopy. These results demonstrate that no chemical change is found, except that carboxylate groups are protonated to carboxylic groups, indicating that fulvic acid is stable as a regenerable absorbent.

Determination of buffering capacity of selected fermented feedstuffs and the effect of dietary acid-base status on ruminal fluid pH

The aim of this study was to evaluate the buffering capacity of some fermented feedstuffs and the effect of dietary acid-base status on ruminal fluid pH. The first experiment was performed with different types (n = 24) of wet and dry fermented feedstuffs to determine the buffering capacity and buffer value index. The buffer value index of wet corn silages was more negative than for dry corn silages account on acid loss during drying. In the second experiment, the effects of different concentrations of lactic acid on base-buffering capacity, buffer value index and indicators of fermentation process were studied in two groups of corn silages (n = 21). Two groups of analyzed values were compared using unpaired t-test. Differences among the groups in base-buffering capacity (P &lt; 0.001) and buffer value index (P &lt; 0.01) were significant. In the third experiment, rumen fluid pH was measured using 8 total mixed rations on 48 lactating dairy cows. In the present study no significant (P &gt; 0.05) correlation was found between ruminal pH and dietary buffer value index. These results confirmed that dietary acid-base status alone is not adequate as a predictor of the need for buffers in the diet of lactating cows. It is the first report about using of buffering capacity determination methods for evaluation of feedstuffs and dietary acid-base status in dairy cows.

Multivariate modeling of MDF panel properties in relation to wood fiber characteristics

Abstract Properties of medium density fiberboard (MDF) panels in relation to wood and fiber characteristics were investigated. Laboratory MDF panels were manufactured from raw fiber materials from black spruce [Picea mariana (Mill.) BSP.], three hybrid poplar clones (Populus spp.), two exotic larch (Larix gmelinii and Larix sibirica), and a mix of spruce, pine, and fir wood chips. The panels were evaluated for modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB), linear expansion (LE), thickness swelling (TS), and water absorption (WA). These properties were analyzed as response variables. As predictor variables, various wood and fiber characteristics were measured, including wood density, pH, base buffering capacity and fiber coarseness. Multiple linear regression analysis was performed to develop functional relationships between panel properties (response variables) and wood fiber characteristics (predictor variables). Ten dummy variables were created and incorporated into the analysis to examine the effects of wood species or type on MDF panel properties. MOR was negatively related to arithmetic fine percentage. MOE was negatively affected by the percentage of small particles (&gt;200 mesh) and wood pH. IB strength was negatively related to arithmetic fine percentage and fiber pH, but positively related to the percentage of small particles (&gt;200 mesh). Wood density affected LE. TS was negatively affected by arithmetic mean fiber length. Arithmetic mean fiber width had a negative effect on panel WA. The presence of dummy variables in the models for MOE, IB and LE indicates that wood fiber characteristics other than those measured in this study significantly affected these panel properties. The study indicates that the refining process can play a significant role in manipulating MDF panel properties.

Proton Binding to Humic Acids from Organic Amendments and Amended Soils by the NICA-Donnan Model

The acid-base properties of humic acids (HAs) are known to significantly affect the acid-base buffering capacity of soils, thus having a marked influence on the speciation of cations in the soil solid and liquid phases. Detailed information on the proton binding behavior of humic-like acids (HALs) from organic amendments and humic acids (HAs) from amended soils is, therefore, of intrinsic interest for the evaluation of the agronomic efficacy and environmental impact of soil amendment. In this work, the acid-base properties of HLAs isolated from sewage sludge (SS) and municipal solid waste compost (MSWC), and HAs isolated from soils amended with either SS or MSWC and the corresponding nonamended control soils were investigated by potentiometric titrations at various ionic strengths (0.01, 0.05, 0.1, and 0.3 M) over the pH range from 3.5 to 10.5. The nonideal competitive adsorption (NICA)-Donnan model that describes proton binding by two classes of binding sites with low and high proton affinity, i.e., carboxylic- and phenolic-type groups, was fit to titration data, and a set of fitting parameters was obtained for each HLA and HA sample. The NICA-Donnan model successfully described the shapes of the titration curves, and highlighted substantial differences in site density and proton-binding affinity between the HLAs and HAs examined. With respect to the nonamended control soil HAs, SS-HLA and MSWC-HLA were characterized by smaller carboxylic-type and phenolic-type group contents, larger affinities for proton binding by the carboxylic-type groups, and smaller affinities for proton binding by the phenolic-type groups. Amendment with SS and MSWC determined a number of modifications in soil HAs, including decrease of acidic functional group contents, slight increase of proton affinity of carboxylic-type groups, and slight decrease of the affinities for proton binding by phenolic-type groups. These effects were more evident in the HA fraction from the SS-amended soil than in the HA fraction from the MSWC-amended soil. Thus, both organic amendments examined can be a considered as a valuable source of organic matter for soil. However, MSWC appears to be an amendment of greater quality producing a smaller impact than SS on proton-binding behavior of soil HA.

Geochemical modelling of bentonite porewater in high-level waste repositories

The description of the geochemical properties of the bentonite backfill that serves as engineered barrier for nuclear repositories is a central issue for perfomance assessment since these play a large role in determining the fate of contaminants released from the waste. In this study the porewater chemistry of bentonite was assessed with a thermodynamic modelling approach that includes ion exchange, surface complexation and mineral equilibrium reactions. The focus was to identify the geochemical reactions controlling the major ion chemistry and acid–base properties and to explore parameter uncertainties specifically at high compaction degrees. First, the adequacy of the approach was tested with two distinct surface complexation models by describing recent experimental data performed at highly varying solid/liquid ratios and ionic strengths. The results indicate adequate prediction of the entire experimental data set. Second, the modelling was extended to repository conditions, taking as an example the current Swiss concept for high-level waste where the compacted bentonite backfill is surrounded by argillaceous rock. The main reactions controlling major ion chemistry were found to be calcite equilibrium and concurrent Na–Ca exchange reactions and de-protonation of functional surface groups. Third, a sensitivity analysis of the main model parameters was performed. The results thereof indicate a remarkable robustness of the model with regard to parameter uncertainties. The bentonite system is characterised by a large acid–base buffering capacity which leads to stable pH-conditions. The uncertainty in pH was found to be mainly induced by the pCO 2 of the surrounding host rock. The results of a simple diffusion–reaction model indicate only minor changes of porewater composition with time, which is primarily due to the geochemical similarities of the bentonite and the argillaceous host rock. Overall, the results show the usefulness of simple thermodynamic models to describe porewater chemistry of expandable clays although significant uncertainties with regard to the effects of swelling and physico-chemical properties of the interstitial water remain.

Effect of fiber source on cecal fermentation and nitrogen recycled through cecotrophy in rabbits.

The influence of fiber source on fiber digestion in rabbits was investigated. Six fibrous feedstuffs with wide differences in chemical composition and particle size were selected: paprika meal, olive leaves, alfalfa hay, soybean hulls, sodium hydroxide-treated barley straw, and sunflower hulls. Six diets were formulated to contain one of these ingredients as the sole source of fiber. To avoid nutrient imbalances, fiber sources were supplemented with different proportions of a fiber-free concentrate, based on soy protein isolate, wheat flour, lard, and a vitamin and mineral mix, to obtain diets containing at least 3% nitrogen and 5% starch. Daily soft feces excretion, and its NDF, and total and microbial nitrogen content were determined in 60 fattening rabbits (10 per diet). Seven days after the last cecotrophy control, the same animals were used to determine weight of stomach, cecum and their contents, and cecal fermentation traits (pH, VFA and ammonia concentrations, and buffer properties of cecal contents). Stepwise regression analysis showed a positive effect (P < .001) on soft feces excretion, total and microbial nitrogen concentrations in soft feces, cecal acidity, and total VFA in the cecum of dietary pectic constituents (2.9, 3.5, 2.5, .9, and 6.6%) and proportion of fine particles (< .315 mm) (1.8, .9, 1.3, .15, and .9%) per each increment of one percentage unit of the independent variables. Proportion of fine particles also increased weight of cecal contents (P < .001). Soft feces excretion and weight of stomach and of its contents increased (P < .001) by 5.2, 2.8, and 10.2% per each percentage unit increment of proportion of large particles (> 1.25 mm). Degree of lignification of NDF decreased total nitrogen concentration in soft feces and cecal VFA concentration (P < .001). Source of fiber affected cecal pH not only by its influence on the cecal concentrations of the final products of fermentation, but also through its effect on the pH of dry cecal contents (P < .001). The latter was negatively correlated with dietary proportion of fine particles, degree of lignification of NDF, and base-buffering capacity of dry cecal contents (r = -.52, -.37, and -.49, respectively). From these results, we conclude that pectic constituent concentration, degree of lignification of NDF, and particle size are the variables that best characterize the influence of the source of fiber on soft feces excretion and cecal fermentation traits in rabbits.

Abatement of acidification in mining lakes in Germany

AbstractOpen‐cast lignite mining has exposed formerly anaerobic layers to the air. Pyrite and marcasite are oxidized to sulfuric acid and iron sulfate, which later hydrolyses to iron hydroxide. When the pit is refilled with groundwater, its pH is 2–3. These geogenically acidified mining lakes are brown, with high iron content. Biological conditions differ greatly from those in most natural lakes and resemble those in sulfur‐acidic lakes impaired by acid rain. The usability of these fish‐free lakes is also restricted for recreational purposes.Neutralization with lime is expensive. The iron‐buffered water has a high base buffering capacity stabilizing at pH 2–4. The complex of potential measures for neutralization comprises: the revegetation of the waste heaps, the hydrological regime and coupled transport processes, the selection of suitable filling water and in‐lake technologies. Desulfurication takes place with sulfidic binding of iron and natural neutralization under locally anaerobic conditions in the reclaimed overburden heaps, in the deep water of mining lakes, in macrophyte stands and in the sediments.Anaerobic conditions should be established within the lakes during stratification periods: in the hypolimnion of eutrophic or the monimolimnion of meromictic lakes. Acidic lakes often are not sufficiently productive to achieve deep‐water oxygen depletion. Measures to increase the stability of stratification may be necessary, for example by installation of barriers to establish an environment suitable for biological neutralization. Carbon sources for microbial desulfurication may be added artificially or autochthonically produced by primary producers. Therefore, a controlled eutrophication may be useful in the initial filling stages of acidic mining lakes.

Influence of Feed Ion Content on Buffering Capacity of Ruminant Feedstuffs In Vitro

In vitro buffering capacity of 52 feeds was measured to determine the buffering capacity range within and among feed types. Feeds were analyzed for dry matter, total ash, minerals (Ca, Mg, K, Na, Cl, N, P, Si, S), pH, titratable acidity and alkalinity, acid-buffering capacity, and base-buffering capacity (milliequivalents of acid or base required to bring .5g dry matter suspended in 50ml distilled deionized water to pH 4 or 9, respectively, divided by total pH change). Buffering capacity was lowest for energy feeds, intermediate for low protein feeds (15 to 35% crude protein) and grass forages, and highest for high protein feeds (>35% crude protein) and legume forages. The concept of diet formulation for a predetermined buffering capacity was tested. Two isonitrogenous and isocaloric diets substantially different from each other in buffering capacity were formulated using ingredients from the pool of 52 feeds. The measured acid-buffering capacity of these diets was similar to their predicted values. Acid buffering capacity was correlated with total cations and total ash. However, simple linear regression was not sufficient to predict accurately acid-buffering capacity from total ash values. Further studies are needed to provide a better estimate of feed-buffering capacity.